Maybe not what you wanna do but - as an old engineer I'd mark up for the other needed holes and drill case after moving mobo out the way - and use suitable sheet metal screws to suit mobo holes - assuming of course that mobo holes are in ''safe'' zones of PCB.
If screws project outside case - no biggie unless esthetics matter. Add spacers to suit too of course - fiber washers or something non conductive.
Not sure what else you can do right now.
